Overboosting ABY

[Glen Chamberlain]

I am pretty new to the whole s2 scene so please forgive my ignorance and be gental with any replys!
I have a 95 ABY that has been chipped at some time but then allegedly set back to normal (still left the adjustable WG spring on) due to it holding the throttle on in gear changes.
Some times when you floor the throttle from low down it seems to hold back, then when it achieves boost the dam thing cuts out then in, out, in, out, you get the picture! The annoying thing it's intermittent. It’s currently misbehaving so I plumbed a boost gauge in and watched the boost on the road. By 2600rpm (or so I remember) 18psi (1.2 bar) was achieved then the drama started. I have done this same test before and had no problems, even got 19psi (1.3 bar) on overboost. All hoses and vac pipes test ok, no leaks. Any idea more than welcome, thanks?

[Greg_S]

are you certain the chip has been removed?

is your wastegate adjustable? To see if the wastegate is set correctly there are directions on pauls S2central.net site

If you un plug the WGFV then the system goes back to mechanical boost of max 0.8bar you can use this as a quick indicator to see if the Wastegate spring is too tight.

I had a similar problem with mine last year and it turned out to be the WGFV valve was sticking and allowing the engine to overboost slightly.

Greg

[Dr H]

I have a car that was superchipped but is now back to standard apparently.

I recently fitted a boost gauge it regularly goes up to 1.3 bar and I have seen it go as high as 1.5 for an instant. The car runs absolutely fine though

Greg did your car show any problem signs of overboost or did you just see high pressure on the gauge?

Is this something I should be concerned about or is my boost gauge just inaccurate? It's a racetech.

Leigh

[Glen Chamberlain]

Originally posted by Greg_S
are you certain the chip has been removed?

is your wastegate adjustable? To see if the wastegate is set correctly there are directions on pauls S2central.net site

If you un plug the WGFV then the system goes back to mechanical boost of max 0.8bar you can use this as a quick indicator to see if the Wastegate spring is too tight.

I had a similar problem with mine last year and it turned out to be the WGFV valve was sticking and allowing the engine to overboost slightly.

Greg

I had a gander in the ECU and all things look original to me but it definately has been opened before. The little blue dots of paint on chips are still there! but bear in mind i dont look in many ECU's to have much to compare with. I have replaced the WGCFV and tried a friends MAF. The lambda was replace at 80K (bosch! now done103k). It does regularly throw up 2413 which I belive to be mixture adjustment? It does sometimes when cold suffer from flat spot? When i've had the problem before i have tried slackening the WG spring in stages untill it wont go any slacker, but still the problem rears it's ugly head.?

[Greg_S]

have you plugged a boost guage up to see what your actually getting?

could it be the MAP sensor on the ECU or a sticky ISV?

[Glen Chamberlain]

Originally posted by Greg_S
have you plugged a boost guage up to see what your actually getting?

could it be the MAP sensor on the ECU or a sticky ISV?

Problem sorted! Even though it had only covered 22K the Bosch Lambda was jaffed!

[Dr H]

Great that you sorted it but.................what knackered the Lambda?

Sorry, don't want to **** on your fire but also don't want your next lambda to go early either.

Anyone know what cause lambdas to go early ?

I found this on the net:

Home or professional auto repairs that have used silicone gasket
sealer that is not specifically labeled "Oxygen sensor safe",
"Sensor safe", or something similar, if used in an area that
is connected to the crankcase. This includes valve covers, oil
pan, or nearly any other gasket or seal that controls engine oil.
Leaded fuel will ruin the O2 sensor in a short time. If a car is
running rich over a long period, the sensor may become plugged up or even destroyed. Just shorting out the sensor output wire will not usually hurt the sensor. This simply grounds the output
voltage to zero. Once the wiring is repaired, the circuit
operates normally. Undercoating, antifreeze or oil on the
*outside* surface of the sensor can kill it.

Leigh